Wastewater Treatment Plant Expansion

Wastewater Treatment Plant Expansion

Capacity increase means being prepared for Owatonna’s future growth

Construction of the Wastewater Treatment Facility Upgrade and Expansion has been progressing since July 2022. 

The project is expected to be completed in 2025. An expansion of Owatonna’s existing wastewater treatment plant was initiated in 2017. The plant has been operating at or above its capacity for the past several years. In 2021, plans got underway to expand the plant from its current capacity of five million gallons per day (MGD) to more than nine MGD, an 80 percent increase to continue meeting the needs of the growing community. 

The project’s original completion date of the end of 2024 has been delayed to 2025 largely due to supply chain issues with electrical components. 

Year 1 Summary - July 2023

The Owatonna Wastewater Treatment Facility (WWTF) is one year into construction of its upgrade and expansion project. At the end of the approximate three-year construction, the WWTF will be nearly double its current capacity which will serve the City’s expected growth over the next 25 years.

The Owatonna WWTF expansion project includes three new buildings as well as upgrades to the existing facility. The first year of construction largely focused on the construction of the three new buildings: the Membrane Bioreactor (MBR) Building, the Fine Screen Building (FSB), and the Solids Thickening Building (STB).

MBR milestones included:

  • August 2022: Excavation for the MBR building, which has the largest footprint of the three new structures. 
  • September 2022: The project’s first concrete pour, the MBR base slab.
  • October 2022: Concrete pours continue for the base slabs of the 7 membrane tanks.
  • November 2022 – March 2023: Concrete walls were poured throughout the winter despite the cold and snowy conditions.
  • April 2023: Deck pour for upper level.
  • May 2023: Tanks tested for water tightness. 
  • June 2023: Precast walls and roofs installed. The MBR building walls are texturized and colored to match the existing tanks onsite.

FSB milestones included:

  • September 2022: Excavation and footings for the tallest new building—FSB which will house three fine drum screens to remove solids larger than 2 millimeters.
  • October 2022: Buried piping around building installation and connection of piping from the Main Lift Station.
  • November 2022: Interior masonry wall installation. 
  • December 2022: Precast walls, floors and roof were set in place. FSB is the tallest new structure and the brick façade blends in nicely to the existing buildings at the WWTF site entrance.
  • January 2023: Concrete slab pours within building.
  • February 2023: Three fine drum screens flown in through the roof and installed on the upper level of FSB.
  • March 2023: Roof installation and plumbing, electrical, and mechanical work within the building.
  • April 2023: Interior painting.
  • May 2023: Interior stairways installation.

STB milestones included:

  • December 2022: Excavation for the STB which is the deepest structure. A temporary earth retention system was installed to support the existing adjacent structures during construction.
  • March 2023: Plumbing and conduits installed and base slab formed.
  • April 2023: Base slab concrete pour.
  • May-June 2023: Concrete wall pours.

Other first-year milestones included scheduling, coordination, and equipment deliveries. With two of the three new structures enclosed, the new equipment is continually being set in place. The next year of construction will start to have a larger impact on the existing WWTF operations which will certainly pose some challenges. However, the implementation of new equipment and processes is an exciting step towards operating the improved facility.